How to Watch the Olympics:This is the first time nearly everyone in the US will have easy access to watch Olympic events live, rather than tape delayed.
Here a full schedule of events.
Click on a sport and see the "My Time" column to see your time.
Beware that Korea is 14+ hours ahead of the US, so an event which starts on a Sunday at 12pm in Korea will air live in the US on Saturday evening.
Our list of ways to watch the 2018 Winter Olympics:

Use an HD antenna:

Your local NBC channel should have some live events airing throughout the day.
Check NBC's TV Listings for the local NBC channel schedule.

Watch on phones & tablets, and watch on your TV with smart apps, a Chromecast, a Roku, a Fire TV, or an Apple TV.

To watch, log in to your streaming TV service and tune to the NBC, NBCSN, CNBC, USA, and Olympic channel provided by the service.
Some of those services have DVR, so you can pause, rewind, and watch delayed.

Or, go to NBC Olympics.com or download the NBC Sports App, and press "Stream Now" next to a live broadcast.
Select your streaming TV service when asked, by choosing Fubo TV, YouTube TV, Sling TV, DirecTV Now, or Playstation Vue.

The cheapest streaming option for non-Cable TV subscribers:

Subscribe to Fubo TV for $20 for your first month.
Includes DVR.
The price rises to $45/mo after the first month, but pay only $20 if you cancel before the first month ends.

Other streaming services:

Sling TV 7-day free trial, then $30/mo for the Blue package with News add-on.
That package gives you access to all Olympic events, including streaming from NBC Sports.com and the NBC Sports apps.
SlingTV charges $5/mo for DVR add-on, making it $35/mo with full pause, rewind, and delayed watching.

YouTube TV 7-day free trial, then $35/mo.
Unlimited DVR included, and up to 6 members of your household get access with their own DVR.
Even if your local NBC station is not included

Update:
One more option.
Olympics.CBC.CA, which is Canada's news channel, is offering free live streaming of prime time events to everyone, even US households.
It appears to only work on a computer (not streaming devices on a TV, and their app is restricted to Canada only), but is a good alternate to NBC.
They say it will be country-restricted to Canada as of tomorrow, but works in the US now.